Neural electrode system with a carrier having a tape spring-type shape

ABSTRACT

A neural probe comprising an array of stimulation and/or recording electrodes supported on a tape spring-type carrier is described. The neural probe comprising the tape spring-type carrier is used to insert flexible electrode arrays straight into tissue, or to insert them off-axis from the initial penetration of a guide tube. Importantly, the neural probe is not rigid, but has a degree of stiffness provided by the tape spring-type carrier that maintains a desired trajectory into body tissue, but will subsequently allow the probe to flex and move in unison with movement of the body tissue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser.Nos. 61/893,603, filed on Oct. 21, 2013 and 61/895,109, filed on Oct.24, 2013.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of devices and methods used forneural interventions. More particularly, the present invention relatesto a neural probe comprising an electrode array of at least one of astimulation electrode and a recording electrode. The electrode array issupported on a carrier having a shape and structure similar to acarpenter's tape spring. The tape spring-type carrier provides theelectrode array with stiffness along a line of trajectory once deployedinto body tissue, but with a degree of flexibility that allows theelectrode array to move with the tissue.

2. Prior Art

Chronic Deep Brain Stimulation (DBS) devices (brain pacemakers) haveemerged in the last decade as a revolutionary new approach to thetreatment of neurological and psychiatric disorders. Conventional DBStherapy involves controllable electrical stimulation through a leadhaving four relatively large electrodes that are implanted in thetargeted region of the brain. While conventional DBS therapy isgenerally safe and effective for reducing cardinal symptoms of theapproved diseases, it often has significant behavioral and cognitiveside effects and limits on performance. Additionally, the therapeuticeffect is highly a function of electrode position with respect to thetargeted volume of tissue, and more specifically, a function of whichneuronal structures are influenced by the charge being delivered. Withconventional electrodes, there are limitations as to how the charge isdelivered and stimulation fields are limited as all of the electrodesites involved with stimulation are positioned along a single axis.

A neural lead or probe that is useful with DBS among a host of otherinterventional procedures is described in U.S. Pat. No. 8,565,894 toVetter et al. The probe has a carrier of a rigid three-dimensionalshape. An electrode array comprising stimulation and recordingelectrodes is supported on the rigid carrier. The distal end of aguiding element is connected to the proximal end of the carriersupporting the electrode array. While the carrier maintains its rigidthree-dimensional shape, the guiding element is maneuverable from afirst three-dimensional shape into a second, different three-dimensionalshape. Since the carrier portion of the neural probe is rigid, as braintissue and the like move, the electrode array is incapable of flexingand shifting to accommodate such movement.

Thus, there is a need for an improved neural intervention system fordeployment of multiple neural probes to provide fine electrodepositioning, selectivity, precise stimulation patterning, and preciselead location. However, the desire for such positional precision shouldnot be so rigid as to be incapable of flexing and bending to accommodatetissue movement. The present invention provides such an improved anduseful neural intervention system for placement of multiple neuralprobes in tissue, particularly brain tissue. That is done by supportingan electrode array on a tape spring-type carrier. The carrier providesan improved degree of stiffness along a line of trajectory once probe isdeployed into body tissue, but allows for a degree of flexibility toaccommodate movement of body tissue surrounding the neural probe.

SUMMARY OF THE INVENTION

Each thin-film neural probe electrode array according to the presentinvention is comprised of multiple metal traces and sites. As many as100 conductive traces and electrode sites can be realized on an arraythat is as narrow as 30 microns and as thin as 6 microns. In order to bestrong enough to be inserted into tissue, however, these neural probeelectrode arrays must be either integrated during fabrication on acarrier that provides strength, or attached to a strengthening carrierpost-fabrication. If the strengthening carrier is stiff, the electrodearray can be inserted into tissue along a desired axial direction of aguiding element. In some cases, however, it is preferable to interfacewith tissue along a trajectory that is off-axis to the initialpenetration of the guiding element. This requires a carrier that candeploy from the guiding element and follow a bend after penetration intobody tissue and then maintain a straight trajectory after bending.

The use of tape spring-type carriers and the appropriate deploymentdevice makes such insertion possible. Tape springs are used in a varietyof deployable structures to serve as hinge mechanisms. An example is acarpenter's tape measure. It has geometric stiffness when extended, butcan be guided around a corner. This is due to the curved cross-sectionof the structure. The normally curved cross-section results in a stiffU-beam structure that allows controllable one-directional axial motion(pulling the tape out or in). When the tape is pushed through a bend,the section of the tape in the bend flattens. As the tape is pushed pastthe bend, the spring returns to its curved U-beam state, again resultingin a stiff beam structure, but pointed axially in a new direction.

Accordingly, the present invention relates to a neural probe comprisingan array of stimulation and/or recording electrodes supported on a tapespring-type carrier. The neural probe comprising the tape spring-typecarrier is used to insert flexible electrode arrays straight intotissue, or to insert them off-axis from the initial penetration of aguide tube. Importantly, the neural probe is not rigid, but has a degreeof stiffness provided by the tape spring-type carrier that maintains adesired trajectory into body tissue, but will subsequently allow theprobe to flex and move in unison with movement of the body tissue.Additionally, an assembly is described to allow deployment of multiplethin-film neural probe electrode arrays from a single guide tube in athree-dimensional arrangement. Formation of the neural probe with thetape spring-type carrier, design of the electrode arrays, and thedeployment mechanism are all described herein.

These and other objects will become apparent to one of ordinary skill inthe art by reference to the following description and the appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a neural intervention system 10according to the present invention.

FIG. 1A is a schematic of the neural intervention system 10 residing inbody tissue 18.

FIG. 1B is an enlarged view of the designated area from FIG. 1A.

FIG. 2 is a schematic of the neural intervention system 10 shown in FIG.1 including deployment channels 14 and neural leads 16.

FIG. 2A is an enlarged perspective view, broken away from FIG. 2,showing outlet ports 22C to 22E at the distal end of the guide tube 12.

FIG. 2B is an enlarged view of deployment port 22C shown in FIG. 2A.

FIG. 3A is a perspective view of the distal portion of the guide tube 12including the deployment channels 14 shown in FIG. 2.

FIGS. 3B and 3C are schematic views of deployment tubes 14 and 24showing exemplary paths of their open conduits 22 and 24 with respect toplanes C-C and D-D aligned with longitudinal axis A-A.

FIG. 4 is a schematic of an exemplary deployment channel 14.

FIG. 4A is a cross-sectional view taken along line 4A-4A of FIG. 4.

FIG. 4B is a cross-sectional view taken along line 4B-4B of FIG. 4.

FIG. 5 is a cross-sectional view of neural probe 16 showing planarelectrodes 36 and 38 supported on opposite sides of a tape spring-typecarrier 40 according to the present invention.

FIG. 5A is a cross-sectional view of a neural probe 16 similar to thatshown in FIG. 5, but with electrodes 36 and 38 having a curved shape.

FIG. 5B is a cross-sectional view of the neural probe 16 shown in FIG.5A, but with only one electrode 36 supported on the tape spring-typecarrier 40.

FIG. 6 is a perspective view of a neural intervention system 10A similarto that shown in FIG. 2 but with the plurality of neural probes 16directly connected to a plunger 48 and push rod 50 as an actuationmechanism.

FIG. 7 is a perspective view of an alternate embodiment of a neuralintervention system 10B according to the present invention connected toan IPG 17.

FIG. 8 is a side cross-sectional view of a neural intervention system10C according to the present invention with deployment channels 54 and56 at different elevational levels along the guide tube 12 and withrespective push rods 62 and 64 for deploying neural probes therefrom.

FIG. 9 is a side elevational view of a roll 100 of tape spring materialfor one manufacturing method according to the present invention.

FIG. 10 is a side cross-sectional view of a neural probe 16 built byaffixing a thin film electrode arrays 36 and 38 to opposed side of thetape spring from the roll 100 shown in FIG. 9.

FIGS. 11 to 17 illustrate another embodiment of a photo-resist processfor manufacturing the tape spring-type carrier 40 of a neural probe 16according to the present invention.

FIGS. 18, 18A and 18B illustrate another embodiment of a process ofmicrostamping, nanoimprinting or fluting of sheet metal formanufacturing the tape spring-type carrier 40 of a neural probe 16according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, a general depiction of one embodiment of aneural intervention system 10 according to the present invention isillustrated in FIGS. 1 and 1A. The neural intervention system 10comprises a guide tube 12 supporting a plurality of deployment channels14 that are configured to direct the delivery of a number of neuralprobes 16 into body tissue 18. Among a host of possible interventionalprocedures, neural intervention system 10 is designed for use in deepbrain stimulation procedures and more specifically, for interface withdeep brain tissue in a three-dimensional manner. The neural interventionsystem 10 may alternatively be used in any suitable environment such aswith the spinal cord, peripheral nerves, muscles, or any other suitableanatomical location.

The guide tube 12 is a conduit shaped structure having a side wall 12Aextending along a longitudinal axis A-A from a distal portion 12B to aproximal end 12C connectable to a chamber 20. While shown having acylindrical shape that is by way of example only. All that is requiredis that guide tube 12 has a sidewall defining a lumen. The chamber 20 isconfigured for attachment to a skull, preferably in a cranial burr-holeof a patient. Thin-film ribbon cables 19 run through the guide tube fromthe neural probes 16 to the chamber 20.

The chamber 20 is where the ribbon cables 19 connect to an electronicsubsystem (not shown) that serves as an interface to any one of a numberof external devices, such as implantable pulse generator (IPG) 17. Otherelectrical subsystems include, but are not limited to, a printed circuitboard with or without on-board integrated circuits and/or on-chipcircuitry for signal conditioning and/or stimulus generation, anApplication Specific Integrated Circuit (ASIC), a multiplexer chip, abuffer amplifier, an electronics interface, an implantable rechargeablebattery, integrated electronics for either real-time signal processingof the input (recorded) or output (stimulation) signals, integratedelectronics for control of the fluidic components, any other suitableelectrical subsystem, or any combination thereof. Alternatively, theskull chamber 20 is not needed and the ribbon cables 19 connect directlyto any one of the above listed external devices.

The guide tube 12 is preferably made of a rigid material that can beinserted into tissue or other substances without buckling and canmaintain a generally straight trajectory through the tissue 18. Thematerial may be uniformly rigid, or rigid only in a particular direction(such as the axial direction). The guide tube material is preferablyplastic (such as a medical grade plastic) or metallic (such astitanium), but may alternatively be any suitable material such as metalor a combination of materials. The distal tube portion 12B includes arounded or curved tip 12D designed to prevent undue trauma to bodytissue as the guide tube is inserted therein. FIG. 3A illustrates analternate embodiment of a sharpened tip 12D′ adapted to penetrate tissueand aid in insertion of the guide tube therein.

It is within the scope of the present invention that the guide tube 12is maneuverable into the tissue in a three-dimensional arrangement. Sucha maneuverable guide tube 12 may include a system of cables, joints,connections, or robotics that is controlled by a user to position theguide tube in a desired position in the tissue. The maneuverable guidetube 12 may also be guidable remotely and/or wirelessly.

The distal portion 12B of the guide tube includes at least one, andpreferably a plurality of deployment channels. Exemplary deploymentchannel 14 (FIG. 4) comprises a proximal channel portion 14A spaced froma distal channel portion 14B. The exemplary deployment channel 14 has alumen 22 extending from a proximal open end 22A adjacent to the proximalchannel portion 14A to a distal open end 22B adjacent to the distalchannel portion 14B. As will be described in greater detail hereinafter,the proximal and distal open ends 22A, 22B are not aligned along acommon axis. Instead, lumen 22 extends from a proximal open end 22Aresiding along a plane B-B aligned substantially perpendicular to thelongitudinal axis A-A of the guide tube 12 to a distal open end 22Bserving as an open port at the guide tube sidewall 12A. Although by wayof example only, the path from the proximal open end 22A to the distalopen end 22B is substantially a right angle.

FIG. 3B illustrates an embodiment where the lumen 22 from proximal openend 22A to distal open end 22B of channel 14 is bisected by an imaginaryplane C-C aligned along axis A-A. FIG. 3C illustrates the lumen path 24of a second exemplary one of the deployment channels 26 deviating from aproximal open end 26A bisected by plane D-D aligned along axis A-A to adistal open end 26B angularly deviating from plane D-D. As seen from theperspective of a plan view looking down on the proximal end 12C of guidetube 12 and along axis A-A, the angular deviation can be in either theclockwise or counter-clockwise directions.

A third exemplary one of the deployment channels 32 has its proximalopen end 32A residing along the imaginary plane B-B alignedperpendicular to axis A-A and with its distal open end 32B exiting theguide tube sidewall 12A so that the lumen follows a path forming asubstantially obtuse angle with respect to axis A-A. A fourth exemplaryone of the deployment channels 34 has its proximal open end 34A residingalong the imaginary plane B-B, but with its distal open end 34B exitingthe guide tube sidewall 12A so that the lumen follows a path forming asubstantially acute angle with respect to axis A-A. Those skilled in theart will readily understand that a deployment channel can provide alumen that follows a path incorporating a combination of those describedwith respect to the first to the fourth exemplary channels 14, 26, 32and 34. According to the present invention, the trajectory of the distalchannel portion defining the distal open end 22B, 32B and 34B rangesfrom about 10° to 180° with respect to axis A-A. Moreover, it is notedthat distal open end 32B is more proximal than distal open end 34B. Thatis even though their respective proximal open ends 32A, 34A reside alongplane B-B.

Thus, the exemplary deployment channels 14, 26, 32 and 34 can be angledin many different orientations. That is for the purpose of introducing aplurality of neural probes 16 into a target body tissue at any one of anumber of trajectories off axis from axis A-A of the guide tube 12. Thisgreatly improves the footprint of deployed electrodes so that multiplespatially separate stimulation and recording channels radiate outwardlyfrom the distal portion 12B of the guide tube. Enhanced deployment ofneural probes 16 makes it possible to spontaneously record neuronalactivity, movement-related activity, or evoked activity as a result ofstimulation from nearby sites. Simultaneously sampled recordings couldbe exploited to increase the speed and accuracy by which data areacquired. With respect to stimulation, this three-dimensionalarrangement of neural probes 16 can be used in either monopolar orbipolar modes to steer current to desired body tissue locations.

FIG. 2A is an enlarged view of the distal end 12D of the guide tube.This view shows that the distal open ends 22B of exemplary deploymentchannel 14 can reside on the distal guide tube end 12D. That is inaddition to or instead of the distal open end of a channel residing onthe cylindrical sidewall 12A as shown in FIG. 2. While it is preferredthat the distal open end of a deployment channel have an elongate shapewith opposed curved sidewalls, that is not necessary. Open end 22C has arectangular shape without curved sidewalls. There is also an open end22D for a deployment channel aligned along the longitudinal axis A-A.

FIGS. 4, 4A, 4B, 5, 5A and 5B illustrate a novel aspect of a neuralprobe 16 according to the present invention. The neural probe 16comprises opposed first and second electrodes 36 and 38 comprising anelectrode array supported by a tape-spring-type carrier 40. The carrier40 is of a metal, preferably selected from tungsten, stainless steel,platinum-iridium, or of a polymeric material, and in an unstressedcondition has a shape similar to a carpenter's tape for a tape measure.The tape spring-type carrier 40 flexes to permit the neural probe 16 toreadily bend, thereby when in a stressed condition collapsing into ashape having a linear cross-section 40A (FIG. 4A) perpendicular to thelength of the carrier as the probe moves along a bend in the lumen 22 ofexemplary deployment channel 14. That portion of the tape spring-typecarrier 40 residing in the proximal portion 14A of the deploymentchannel 14 adjacent to the proximal open end 22A has the concave tapespring-type shape 40B (FIG. 4AB). Similarly, that portion of the carrier40 residing in the distal portion 14B of the deployment channel adjacentto the distal open end 22B and extending out therefrom has re-assumedthe tape spring shape. The tape spring-type shape of the carrier 40provides the neural probe 16 with a degree of linear rigidity along thetrajectory of the distal channel portion 14B and outwardly therefromthat is not available with prior art probes.

FIG. 4B shows that the curved cross-sectional shape of the tapespring-type carrier 40 can be concave having a focal point 42 residingoutside plane E-E extending through the carrier's opposed ends. Thecurve cross-sectional shape of the tape spring-type carrier can also bethat of a parabola.

FIGS. 5, 5A and 5B show the tape spring-type carrier 40 sandwichedbetween opposed polymeric layers 40A and 40B. If the carrier 40 is of apolymeric material, then layers 40A and 40 are of a different polymericmaterial. Electrode 36 is exemplary of a stimulation electrode whileelectrode 38 is exemplary of a recoding electrode. The stimulationelectrode 36 is configured for electrical stimulation of biologicaltissue and recording electrode 38 is configured for recording ofbiological activity from biological tissue. The stimulation electrode 36is sandwiched between opposed dielectric layers 37A and 37B. Likewise,recording electrode 38 is sandwiched between opposed dielectric layers39A and 39B. The electrode sites 36, 38 are preferably metal such asiridium, platinum, gold, but may alternatively be any other suitablematerial. Polyimide, parylene, inorganic dielectrics such as siliconcarbide or aluminum oxide, or a composite stack of silicon dioxide andsilicon nitride is preferably used for the dielectric layers 39A, 39B.

The enlarged portions 36A and 38A depict electrical interconnectsrunning the length of the neural probe. In an alternate embodiment (notshown) interconnects 36A, 38A are of a lesser cross-section than therespective electrodes 36, 38. The conductive interconnects 36A, 38A arepreferably metal or polysilicon, but may alternatively be any othersuitable material. Interconnects 36A and 38A preferably terminate withelectrical contacts or bond pads (not shown) at their proximal ends.That is for electrical connection of the electrodes 36, 38 to externalinstrumentation and/or hybrid chips, such as depicted by IPG 17 inFIG. 1. For more detail regarding suitable configurations for electrodesand interconnects for use with neural probes 16, reference is made toU.S. Pat. No. 7,941,202 to Hetke et al., which is assigned to theassignee of the present invention and incorporated herein by reference.

FIG. 5A shows the entire electrode structure having a curved shapemimicking that of the tape spring-type carrier. This is contrast to theelectrode structure shown in FIG. 5 having generally planar electrodefaces. FIG. 5B shows an electrode supported on only one side of the tapespring-type carrier 40.

In one exemplary embodiment of the neural probe 16 shown in FIGS. 1, 1Aand 1B, the electrode array preferably includes sixty-four stimulationelectrodes 36 and thirty-two recording electrodes 38 positioned aroundand along the tape spring-type carrier 40. Each stimulation electrodesite 36 has a surface area of preferably 0.196 mm² (diameter=500 μm),but may alternatively have any suitable surface area or shape. Eachrecording electrode site 38 has a surface area of preferably 0.00196 mm²(diameter=50 μm), but may alternatively have any suitable surface areaor shape. Stimulation sites are also preferably spaced at 750 μm in theaxial direction (center-to-center) and positioned at sixteen successivelocations. Between each row of stimulation electrode sites 36, tworecording electrode sites 38 are preferably positioned on opposite sidesof the tape spring-type carrier 40. The position of each recordingelectrode site pair 38 preferably shifts ninety degrees betweensuccessive depths. Alternatively, there may be any suitable number ofstimulation sites 36 and recording electrode sites 38, and thestimulation electrode sites and recording sites may alternatively bepositioned in any other suitable arrangement.

Referring back to FIG. 2A, the enlarged views of deployment opening 22C,22D and 22E are designed with central axes aligned along a desiredtrajectory line. The trajectory lines come out of the page and aredepicted by the respective points 22C′, 22D′ and 22E′. The respectiveaxes are centered between the opposed major and minor sidewalls of theopening. FIG. 2B is an enlarged view of representative deploymentopening 22C showing opposed major sidewalls 23A and 23B and opposedminor sidewalls 23C and 23D. Axis 22C′ is centered therein andrepresents the trajectory a neural probe 16 comprising the tapespring-type carrier 40 of the present invention would take after havingbeen deployed out from the opening 22C. Representative trajectories22B′, 22C′ and 22D′ are also shown in FIG. 2.

With further reference to FIG. 2, the neural probes 16 are connected toa manifold 44. Thin-film ribbon cables 19, which connect from themanifolds 44 to an electronic subsystem (not shown), serve as aninterface to any one of a number of external devices, such asimplantable pulse generator (IPG) 17 (FIGS. 1 and 7). The probes 16comprising the tape spring-type carrier 40 extend distally from themanifold 44 and are spaced at even or uneven intervals from each other.Moreover, the guide tube 12 can support more than one manifold/neuralprobe assembly. Two such assemblies 46, 48 are illustrated, but that isby way of example. In any event, the neural intervention system 10 isconstructed with the probes pre-registered with their respectivechannels. As previously discussed, FIG. 3A, which is similar to FIG. 2,illustrates that the proximal open ends of the plurality of deploymentchannels are located along common plane B-B, substantially perpendicularto axis A-A. The respective proximal open channel ends are arranged inconcentric circles, the outer circle 50 corresponding to the firstmanifold/neural probe assembly 44 and the inner circle 52 correspondingto the second manifold/neural probe assembly 46. The respective distalends of the probes 16 are received in the proximal open ends of thechannels 14.

FIG. 2 further shows an actuation mechanism for deploying the pluralityof neural probes 16. The actuation mechanism includes a plunger 48connected to the first and second manifold/neural probe assembly 44, 48.The distal face of plunger 48 has grooves (not shown) that are sized andconfigured to receive the upper edges of the respective manifolds 44therein. The opposite face of the plunger 48 supports a push rod 50. Thepush rod extends to the proximal end 12C of the guide tube and has alength that is sufficient for a user to grasp and manipulate to move theplurality of probes 16 through their respective deployment channels andout the open ends thereof. The neural probes 16 are of a sufficientlength that with the plunger 48 moved distally along the tube 12 untilthe manifolds 44 are adjacent to the proximal open ends of thedeployment channels, the probes extend through the exemplary deploymentchannels 14, 26, 32 and 34 and out the distal open ends thereof topenetrate tissue at distances sufficient to provide effectivestimulation or recording capability. While two manifold/neural probeassemblies are shown in FIG. 2, it is within the scope of the presentinvention that three or more such assemblies can be fitted into a singleguide tube 12.

FIGS. 1A and 1B illustrate the guide tube 12 inserted into tissue 18with a plurality of neural probes 16 deployed in a three-dimensionalarrangement into the tissue. The tape spring-type carrier 40 of thepresent invention shuttles the neural probes 16 into tissue or othersubstances in a straight-line or radial direction once the probe hasexited the distal open end of its deployment channel. Moreover, thecarrier 40 may include a sharpened end 16A adapted to penetrate tissueand aid in insertion of the neural probe 16 including the carrier 40into tissue at trajectories off axis from that of the penetrating guidetube 12. Importantly, the carrier 40 is not a rigid structure. Instead,the carrier has sufficient stiffness to follow a desired trajectorydictated by the trajectory axis of one of previously described exemplaryopens 22C, 22D and 22E, but that will move in response to movement ofthe tissue into which the probe 16 has been deployed. That helps toprevent undue trauma to the body tissue while maintaining a desireddegree of stimulation and recording efficacy.

FIG. 6 illustrates another embodiment of a neural intervention system10A according to the present invention. System 10A is similar to thatshown in FIG. 2 except that the actuation mechanism for deploying theplurality of neural probes 16 does not include a manifold. Instead, theneural probes 16 are individually directly connected to the plunger 48connected to the push rod 50. A thin-film ribbon cable 19, whichconnects from the manifolds 48 to an electronic subsystem (not shown),serves as an interface to any one of a number of external devices, suchas implantable pulse generator (IPG) 17 (FIGS. 1 and 7).

FIG. 7 illustrates another embodiment of a neural intervention system10B according to the present invention. System 10B is similar to thesystem 10 shown in FIG. 1 except that the guide tube 12 has a branchedportion 12E extending from the proximal guide tube end 12C. The branchedtube portion 12E houses the ribbon cables (not shown, but similar tothose designated as 19 in FIG. 1A) connected to IPG 17 as an exemplaryelectronic subsystem. There is also an open port 52 where the proximalguide tube portion 12C meets the branched tube portion 12E. Port 52provides an exit for push rod 50 of the actuation mechanism fordeploying the plurality of neural probes 16 into tissue 18.

FIG. 8 illustrates a further embodiment of a neural intervention system10C. This embodiment shows that it is within the scope of the presentinvention that guide tube 12 can support a first, and preferably aplurality of first deployment channels 54 at a more distal location thana second, and preferably a plurality of second deployment channels 56.The first deployment channels 54 have their proximal ends 54A supportedby plate 58 connected to an inner surface of the guide tube sidewall12A. The distal open ends 54B provide a port in the guide tube sidewall12A adjacent to the distal tube portion 12D. The proximal ends 56A ofthe second deployment channels 56 are likewise supported by a secondplate 60 connected to the inner guide tube sidewall. Their distal openends 56B provide a port in the guide tube sidewall 12A adjacent to theproximal tube end 12C.

A firsts push rod 62 serving as an actuation mechanism extends throughan opening 60A in the second plate 60 and is connected to the proximalends of neural probes 16 in registry with the first deployment channels54. A second push rod 64 serves as an actuation mechanism for deployingneural probes 16 in registry with the second deployment channels 56. Itis noted that the proximal ends of first deployment channels 54 areradially closer to the longitudinal axis A-A than the proximal ends ofthe second deployment channels 56. That is to provide clearance so thatthe first push rod 62 does not interfere with the second push rod 64.

It will be understood by those skilled in the art that the structure ofpush rods 62 and 64 is for the purpose of illustration only. Otherstructural configurations are within the scope of the present invention.Moreover, while first and second sets of deployment channels 54, 56 areshown, it is within the scope of the present invention that there can betwo, three or more deployment channels delineated from each other not bywhere their respective distal open ends exit the guide tube sidewall12A, but where their proximal open ends reside inside the guide tubewith respect to each other.

FIGS. 9 and 10 illustrate one method of making a neural probe accordingto the present invention. A metal or composite tape spring 40 isprovided in a roll. The tape spring material is rolled out andfabricated to a desired shape. The electrode structures 36 and 38 shownin FIGS. 5, 5A and 5B are then affixed, such as with a suitable medicalgrade adhesive, to one or both sided of the tape spring-type carrier 40.

FIGS. 11 to 17 illustrate the steps for forming a neural probe 16incorporating a tape spring-type carrier 40 according to a secondembodiment of the present invention.

FIG. 11 shows a photo-resist material 102 is deposited on amanufacturing substrate 104. The photo-resist 102 is patterned in ashape similar to that desired for the product tape spring-type carrier40. The substrate 104 is preferably made of glass or silicon, but mayalternatively be made from any other suitable material. The substrate104 may be flexible, rigid, or semi rigid depending on themicrofabrication tooling (organic electronics equipment can increasinglyuse flexible substrates such as in roll-to-roll manufacturing, whereasIC and MEMS microfabrication equipment use a rigid silicon substrate).The substrate 104 has a thickness ranging from about 200 microns toabout 925 microns, preferably greater than 500 microns.

The photo-resist material 102 is preferably a thin film of gel,photoresist, or other transparent or semi-transparent organic mediumthat can be patterned onto the substrate 104. The photo-resist film 102is preferably at least semi-transparent to allow passage of light from aUV light source through the photoresist material. For positivephotoresists, the area that is exposed to the UV light can be developedaway in a developer. For negative photoresist, polymer at the area thatis exposed to the UV light forms strong chemical bonds that canwithstand a developer, while the unexposed area can be developed away ina developer. The photo-resist film 102 can be deposited, patterned,exposed to UV light, and developed in any suitable thin film technique.

FIG. 12 illustrates that the photoresist 102 is subjected to heat sothat it flows and forms a curved or parabolic upper surface 102A to thesubstrate 104 of a shape approximating the final tape spring-typecarrier shape. Then, the heated photoresist is subjected to a DeepReactive Ion Etching (DRIE) 106 process to duplicate the photoresistpattern 102A on the substrate upper surface 104A. After the DRIEprocess, the resulting structure will be cleaned by oxygen plasma orstandard organic and inorganic wet cleaning process.

FIG. 13 shows that after cleaning, a metal or polymeric carrier layer110 is deposited on the upper or outer surface 104A of the substrate.The carrier layer 110 can be deposited using any suitable thin film,semiconductor, microelectromechanical systems (MEMS) manufacturingtechnique or other microfabrication process, such as physical vapordeposition. Exemplary techniques and processes include evaporation andsputtering deposition. The carrier layer 110 preferably includes thermalconductive or electrical conductive material such as of platinum (Pt) orplatinum-iridium, iridium oxide, titanium nitride, or any other metal,metal oxide, shape memory alloy, or conductive polymer having suitableelectrically conductive properties. The carrier layer 110 can also be ofa polymeric material, such as of polyimide, but may alternatively bemade from any other suitable material. Moreover, the carrier layer 110can be of a resorbable material, which is resorbed into tissue after aperiod of time. With the carrier supporting an electrode array, uponresorption, the electrode array is left to float freely in the brain orother suitable tissue or material. The bioresorbable polymer ispreferably polyglycolide or polylactide, but may alternatively be madefrom any suitable bioresorbable material.

The carrier layer 110 is shown as a continuous layer and can bepatterned (FIG. 14) using any suitable wet etch or dry etch technique.The mask (not shown) is a photodefined resist or any other maskingmaterial patterned directly or indirectly using standardphotolithography techniques. After the carrier layer 110 is patterned,excess metal or polymeric layer is etched away, leaving the pattern ofthe tape spring behind. A lift-off process, as is well known to thoseskilled in the art, can also be used to leave the tape spring pattern.

FIG. 15 illustrates that polydimethylsilisane (PDMS) as an exemplarytransfer material 112 is spun onto the carrier patterns 110 followed bymounting a second manufacturing substrate 114 thereon. Polyimide can beused at this step instead of PDMS. In this case, electrodes can befabricated on the polyimide film before undergoing the layer transferonto a new carrier.

The original manufacturing substrate 104/108 is removed exposing curvedinner surfaces 110A of the patterned tape spring-shaped material. Thiscan be achieved by wet or dry etching technique.

FIG. 16 shows that the second manufacturing substrate 114 is flippedupside down, and a polyimide material 116 is spun coated onto theexposed curved inner surfaces 110A.

FIG. 17 illustrates that a photolithography process is used to definethe shape of the thusly fabricated tape spring-type carrier 40 withpolyimide layers 40A and 40B coated on both sides. The result is thetape spring-type carrier 40 sandwiched between polymeric layers 40A, 40Bshown in FIGS. 5, 5A and 5B.

FIGS. 18, 18A and 18B illustrate the steps for forming a neural probe 16incorporating a tape spring-type carrier 40 according to a thirdembodiment of the present invention.

FIG. 18 shows a sheet of metal 200 including patterned carrier 40 andregistration patterns 202. The registration patterns 202 provide forregistering the carrier sheet 200 to the electrode manufacturingsubstrate as shown in FIGS. 5, 5A and 5B. Subsequent photolithographicprocesses will embed the carriers 40 between polymer electrodes.Microstamping is one exemplary process using a laser to engrave thesheet 200 with a patterned shape of the tape spring-type carrier.

Thermoplastic nanoimprint lithography (T-NIL) is another suitableprocess. Thermoplastic nanoimprint lithography uses a thin layer ofimprint resist thermoplastic polymer spun-coated onto a substrate (notshown). Then the substrate, which has topological patterns of the tapespring shape, is brought into contact with the polymeric sheet 200 andthe mold and sheet are pressed together under pressure. When heated upabove the glass transition temperature of the polymer sheet 200, thepattern on the mold is pressed into the softened polymer. After cooling,the mold is separated from the sheet 200 and the tape spring patternresist is left on the sheet 200. A pattern transfer process (reactiveion etching, normally) is used to transfer the pattern in the resist tothe underneath sheet 200.

Alternatively, cold welding between two metal surfaces can be used totransfer low-dimensional nanostructured metal without heating(especially for critical sizes less than −10 nm) onto sheet 200. Becausethe cold welding approach does not require heating, it has the advantageof reducing surface contact contamination or defect due normallyattendant heating-related processes.

Other methods for shaping metal into a concave/convex structure suitablefor manufacturing a tape spring-type carrier according to the presentinvention include fluting, extrusion, and electrostatic dischargemicromachining (ESD).

The plurality of thusly produced tape spring-type carriers 40 connectedto a manifold 44 (four shown carrier are shown in the subassemblydesignated 204 in FIG. 18A) are built into neural probes 16 according toone of the exemplary structures shown in FIGS. 5, 5A and 5B. Themanifolds 40 are similar to those depicted in FIG. 2.

The tape spring-type carrier 40 may further extend the functionality ofthe system 10 by providing fluidic channels through which therapeuticdrugs, drugs to inhibit biologic response to the implant, or any othersuitable fluid may be transmitted. This provides for the precisedelivery of specific pharmaceutical compounds to localized regions ofthe body, such as the nervous system, and could facilitate, for example,intraoperative mapping procedures or long-term therapeutic implantdevices. The fluidic channels may also provide a location through whicha stiffener or stylet may be inserted to aid with implantation.Alternatively, the carrier may further include a separate lumen throughwhich the stiffener or stylet may be inserted.

Thus, a plurality of neural probes 16 constructed with a tapespring-type carrier 40 according to the present invention and deployedfrom an exemplary guide tube 12 increases the effective site area toallow increased charge injection while maintaining safe electrochemicaland biological limits. This will enable, for example, precise currentsteering to selectively stimulate neural structures. The thusly deployedneural probes can be used to establish one or more tunable neuralinterface region for the device. Multiple neural interface regions canbe overlapping or non-overlapping. Additionally, at least two electrodesites from each probe 16 may be grouped to form a larger composite sitethat enables tuning the neural interface region for recording and/orstimulation. This grouping of sites can be through intrinsic connectionof the site traces, or it can be through external connections forreal-time tuning.

While this invention has been described in conjunction with preferredembodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, the present invention is intended to embrace all suchalternatives, modifications and variations that fall within the broadscope of the appended claims.

What is claimed is:
 1. A neural probe, which comprises: a tapespring-type carrier having a carrier thickness extending along a carrierlength between a first major surface of the tape spring-type carrier anda second major surface of the tape spring-type carrier extending from aproximal carrier end to a distal carrier portion having a distal carrierend, wherein the first major surface is opposite the second majorsurface; wherein the tape spring-type carrier has a stiff, curved U-beamstate along the carrier length when in an unstressed condition; wherein,when a section of the tape spring-type carrier is moved through a bend,the section in the bend flattens; wherein, when the section of the tapespring-type carrier is moved past the bend, the section returns to thestiff, curved U-beam state; and wherein the proximal carrier end iselectrically connectable to a source of electrical energy; a firstpolymeric layer; a second polymeric layer, wherein the tape spring-typecarrier is sandwiched between the first polymeric layer and the secondpolymeric layer such that the first polymeric layer and the secondpolymeric layer contact the first major surface and the second majorsurface, respectively; and at least one electrode configured forelectrical stimulation of body tissue or recording of biologicalcharacteristics supported on the tape spring-type carrier, wherein theat least one electrode is supported on at least one of the first andsecond major surfaces.
 2. The neural probe of claim 1 wherein, when inan unstressed condition extending in a substantially axial direction,the tape spring-type carrier has a curved cross-section perpendicular tothe carrier length.
 3. The neural probe of claim 1 wherein, when in astressed condition bent out of alignment with an axial direction, thetape spring-type carrier has a linear cross-sectional shapeperpendicular to the carrier length.
 4. The neural probe of claim 2wherein, when in the unstressed condition extending in the substantiallyaxial direction, the first major surface of the tape spring-type carrierhas a concave cross-sectional shape and the second major surface of thetape spring-type carrier has a convex cross-sectional shape.
 5. Theneural probe of claim 4 wherein, when in the unstressed conditionextending in the substantially axial direction, the first major surfaceof the tape spring-type carrier has a parabolic cross-sectional shape.6. The neural probe of claim 2 wherein, when in the unstressed conditionextending in the substantially axial direction, the tape spring-typecarrier has a shape similar to a carpenter's tape for a tape measure. 7.The neural probe of claim 1 wherein the tape spring-type carrier made isof a metal.
 8. The neural probe of claim 1 wherein the tape spring-typecarrier is made of a polymeric material that is different from the firstpolymeric layer and the second polymeric layer.
 9. The neural probe ofclaim 7 wherein the at least one electrode includes a first electrodeand a second electrode and further comprising: a first pair ofdielectric layers, wherein the first electrode is sandwiched between thefirst pair of dielectric layers with one dielectric layer of the firstpair of dielectric layers contacting the first polymeric layer; and asecond pair of dielectric layers, wherein the second electrode issandwiched between the second pair of dielectric layers with onedielectric layer of the second pair of dielectric layers contacting thesecond polymeric layer.
 10. The neural probe of claim 1 wherein the atleast one electrode is sandwiched between opposed dielectric layers, oneof the dielectric layers contacting the first polymeric layer supportedon the first major surface.
 11. The neural probe of claim 10 wherein thedielectric layers are selected from the group consisting of polyimide,parylene, silicon carbide, aluminum oxide, silicon dioxide, and siliconnitride.
 12. The neural probe of claim 1 wherein the at least oneelectrode is of a metal selected from the group consisting of iridium,platinum, gold, and alloys thereof.
 13. The neural probe of claim 1wherein the distal carrier end is pointed.
 14. A method for providing aneural probe, comprising the steps of: providing a tape spring-typecarrier having a carrier thickness extending along a carrier lengthbetween a first major surface of the tape spring-type carrier and asecond major surface of the tape spring-type carrier that is oppositethe first major surface, the tape spring-type carrier extending from aproximal carrier end to a distal carrier portion having a distal carrierend, wherein the proximal carrier end is electrically connectable to asource of electrical energy; wherein the tape spring-type carrier has astiff, curved U-beam state along the carrier length; and wherein thetape spring-type carrier is sandwiched between a first polymeric layerand a second polymeric layer such that the first polymeric layer and thesecond polymeric layer contact the first major surface and the secondmajor surface, respectively; and supporting at least one electrodeconfigured for electrical stimulation of body tissue or recording ofbiological characteristics on at least one of the first and second majorsurfaces; moving a section of the tape spring-type carrier through abend, wherein the section in the bend flattens as the section movesthrough the bend; and moving the section past the bend, wherein thesection returns to the stiff curved U-beam state when the section hasmoved past the bend.
 15. The method of claim 14 wherein, when in anunstressed condition extending in a substantially axial direction, thetape spring-type carrier has a curved cross-section perpendicular to thecarrier length.
 16. The method of claim 14 wherein, when in a stressedcondition bent out of alignment with an axial direction, the tapespring-type carrier has a linear cross-sectional shape perpendicular tothe carrier length.
 17. The method of claim 15 wherein, when in theunstressed condition extending in a substantially axial direction, thefirst major surface of the tape spring-type carrier has a concavecross-sectional shape and the second major surface of the tapespring-type carrier has a convex cross-sectional shape.
 18. The methodof claim 17 wherein, when in the unstressed condition extending in asubstantially axial direction, the first major surface of the tapespring-type carrier has a parabolic cross-sectional shape.
 19. Themethod of claim 14 wherein, when in an unstressed condition extending ina substantially axial direction, the tape spring-type carrier has ashape similar to a carpenter's tape for a tape measure.
 20. The methodof claim 14 including selecting the tape spring-type carrier from thegroup consisting of tungsten, stainless steel, and platinum-iridium. 21.The method of claim 14 including providing the tape spring-type carrierof a polymeric material.
 22. The method of claim 20 includingsandwiching the tape spring-type carrier between opposed polymericlayers contacting the first major surfaces.
 23. The method of claim 14including sandwiching the at least one electrode between opposeddielectric layers, one of the dielectric layers contacting a polymericlayer supported on one of the first and second major surfaces.
 24. Themethod of claim 23 including selecting the dielectric layers from thegroup consisting of polyimide, parylene, silicon carbide, aluminumoxide, silicon dioxide, and silicon nitride.
 25. The method of claim 14including selecting the at least one electrode from the group consistingof iridium, platinum, gold, and alloys thereof.
 26. The method of claim14 including providing the tape spring-type carrier by one of the groupconsisting of a photo-resist process, a micro-stamping process, athermoplastic nanoimprinting lithography process, a fluting process, anextrusion process, and an electrostatic discharge micromachiningprocess.
 27. The method of claim 14 including providing the tapespring-type carrier with at least one fluid channel extending from theproximal carrier end to the distal carrier portion.